Add opt-in automatic Go version detection on directory change

[Copilot]

When changing between project directories with different .go-version files, GOROOT and GOPATH remain static until the shell is reloaded. While shims detect the correct version, tools relying on these environment variables see stale values.

Changes

• libexec/goenv-init: Added shell hook generation when GOENV_AUTOMATICALLY_DETECT_VERSION=1

  • Zsh: Injects function into chpwd_functions array
  • Bash/KSH: Appends function to PROMPT_COMMAND
  • Fish: Adds function with --on-variable PWD trigger
  • Each hook calls eval "$(goenv rehash --only-manage-paths)" to update environment

• test/goenv-init.bats: Added 9 tests covering hook injection behavior across shells

• Documentation: Updated ENVIRONMENT_VARIABLES.md and INSTALL.md with usage instructions

Usage

Add before eval "$(goenv init -)":

export GOENV_AUTOMATICALLY_DETECT_VERSION=1

Shell hooks automatically update GOROOT/GOPATH on directory change. Feature is opt-in to avoid performance impact for users who don't need it.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Switching directories doesn't change go version</issue_title>
<issue_description>👋🏻

I use https://www.warp.dev/ with a Zsh shell and a https://starship.rs/ prompt (I also use Zoxide for switching directories but the reported issue happens even with standard cd).

I'm finding that when I switch between project directories (where each project has its own .go-version file and are set with different Go versions), that changing directory doesn't trigger the go binary to be the expected version.

Here is my ~/.zshrc configuration:

if [ ! -d "$HOME/.goenv" ]; then
  git clone https://github.com/syndbg/goenv.git ~/.goenv
fi
export GOENV_ROOT="$HOME/.goenv"
export PATH="$GOENV_ROOT/bin:$PATH"
eval "$(goenv init -)"
export PATH="$GOROOT/bin:$PATH"
export PATH="$PATH:$GOPATH/bin"

At the time of reporting this issue, I'm using the latest release:

$ goenv --version
goenv 2.0.6

If I open up a new terminal instance at my home directory ~/ and run which go I see:

/Users/integralist/.goenv/versions/1.20.0/bin/go

This aligns with goenv global.

Now if I cd into a project directory with a .go-version file containing 1.20.2 and re-run go version I'll still see the global Go 1.20.0 being used. If I reload my shell scripts (e.g. source ~/.zshrc) then running both which go and go version will now report the expected 1.20.2 version.

Now if I cd into another project with a .go-version file containing 1.18.5 and re-run go version I'll still see the previous Go version 1.20.2 being used. If I reload my shell scripts (e.g. source ~/.zshrc) then running both which go and go version will now report the expected 1.18.5 version.</issue_description>

<agent_instructions>How would you approach this?</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@ChronosMasterOfAllTime @Integralist that isn't a fork, rather a whole new implementation relying on a golang-compiled CLI tool using goreleaser.

• Fixes Switching directories doesn't change go version #294

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